The French environment minister said yesterday a massive explosion that destroyed a chemical plant in Toulouse last month, killing 29 people and injuring more than 2,000, could have been a terrorist attack.

The remark by Yves Cochet followed the revelation that one of the men found dead on the site of the AZF fertiliser plant in the southern French city had a police record and known Islamic fundamentalist sympathies.

While the Toulouse prosecutor heading the inquiry has consistently said he is "99% certain" the blast was an accident, several leading French scientists have pointed out that the chemical involved - ammonium nitrate - is exceptionally stable and was highly unlikely to have exploded spontaneously.

"A new piece of information reached us today which shows there might have been a terrorist origin" to the blast, Mr Cochet said. But he added the government was not ruling out any cause.

Judicial sources yesterday confirmed that police had identified one of the dead inside the plant as Hassan Jandoubi, 35, a French national born in Tunisia. He was reportedly dressed in several layers of clothing "in the manner of kamikaze fundamentalists".

Jandoubi was known to police as the suspected ringleader of a gang trafficking stolen cars between France and Germany. He was also an active member of a mosque in the Toulouse suburbs where he was "initiated to fundamentalism 10 months ago", a French news magazine reported.

While he was allegedly one of a group of known Islamic radicals seen celebrating last month's terror attacks in the US, his name does not apparently feature on lists of fundamentalist terrorist suspects maintained by Interpol, the French intelligence service and the counter-espionage agency DST.

Jandoubi, who worked for a subcontractor responsible for maintaining and loading the trucks that carried ammonium nitrate away from the site, had started at the plant five days before the explosion.

Witnesses have told police that on September 20, the day before the blast, they saw him arguing angrily with at least one truck driver who had decorated his cabin with a miniature Stars and Stripes out of sympathy with the victims of the September 11 attacks.

On the day of the blast, Jandoubi was working in hangar 10, 30 yards from hangar 221 whose stock of 200-300 tonnes of ammonium nitrate exploded at 10.17am. Windows were blown out in Toulouse city centre three miles away, 10,000 buildings were damaged, 600 houses or apartments destroyed, and 1,400 families left homeless. Nearly 400 people remain in hospital.

Police were initially intrigued by the fact that Jandoubi was found with a mobile phone fitted with a stolen card. Their interest was further aroused by his autopsy, carried out by a doctor who had worked in the Middle East for the international aid organisation Médecins du Monde and who noted that Jandoubi was wearing two pairs of trousers and four pairs of underpants. The doctor said this reminded her "of the apparel worn by some Islamic militants going into battle or on suicide missions".

French media have claimed the police were barred by the chief prosecutor, Michel Bréard, from searching Jandoubi's flat until five days after the explosion. When they gained access to his home, the judicial source said the police had been unable to find any trace of him there.

"Apparently everything had been cleared out," the source said. "There were none of his clothes, none of his personal effects, not even any photos of him. The woman he lived with said she had thrown everything out straight away because she could not bear to be reminded of him."

Jandoubi's unidentified girlfriend, who has been interviewed three times, reportedly told police that he habitually wore several pairs of underpants because "he was very thin, and he was obsessed with the idea that his backside was too small".